Most antimicrobial hand wash formulations exhibiting broad-spectrum activity contain surfactants, active ingredients, or both. Surfactants are employed, in part, to help solublize the active ingredients, and to make them useful in the formulation. The surfactants are typically selected from anionic, non-ionic, amphoteric, quaternary ammonium, and amine oxide surfactants. As is generally appreciated, all of these classes of surfactants have their advantageous and disadvantageous properties. For example, quaternary ammonium compounds are compatible with phenol active ingredients (e.g., triclosan and pcmx), but do not foam to a great extent. Amphoteric surfactants and amine oxides are expensive compared to other surfactant classes. The active ingredients for which the surfactants are chosen are typically selected from bisguanidines, diphenyl compounds, quaternary ammonium compounds, benzyl alcohols, trihalocarbanilides, iodine containing compounds, ethoxylated phenols, and phenolic compounds such as triclosan (2,3,4′-trichloro-2′-hydroxydiphenylether) and parachlorometaxylenol (pcmx). There are numerous limitations to using active ingredients when used in conjunction with surfactants. Because many types of surfactants, typically anionic, amphoteric and non-ionic surfactants, deactivate active ingredients, it has been found necessary to employ surfactant combinations to achieve desired properties.
Although compatible with numerous active ingredients, amine oxides and quaternary ammonium compounds are expensive and yield formulations with sub-par aesthetic properties. Phenolic active ingredients are only sparingly soluble in water therefore requiring solvents, such as propylene glycol, and hydrtropes, such as sodium xylene sulfonate and the primary surfactants are required to dissolve the insoluble compounds. Solvents and hydrotropes are usually detrimental to the final formulation, either because they increase cost or increase irritancy. In order to avoid the negative affects of solvents and hydrotropes the solution can be heated to dissolve the phenolic active ingredient, but this requires large amounts of energy and an extended manufacturing time. A hand wash that is low in solids would offer the advantages of reduced cost combined with a probable reduction in irritation through minimizing the use of irritating surfactants.
It might be desirable to provide antimicrobial hand wash formulations that foam. When foaming is desired, it has been found that high-foaming amphoteric and non-ionic surfactants are the preferred surfactants, but most of them are incompatible with, and even deactivate, phenolic compounds such as triclosan, making their use with this active ingredient less desirable. Amine oxides are commonly used primary surfactants in antimicrobial hand washes because they do not inhibit the efficacious properties of the active compound. However, amine oxides cost significantly more than some other amphoteric and non-ionic surfactants. Thus, there exists a need in the art for a low cost antimicrobial hand wash formulation that includes a primary surfactant that does not negatively impact the efficacy of the active ingredient(s).